Wobble plate arrangement for a compressor

ABSTRACT

A wobble plate arrangement ( 1 ) for a swash plate compressor comprises a swash plate ( 4 ) on which a wobble plate ( 5 ) is rotatably mounted. At least one antifriction bearing ( 7 ) is located between the swash plate ( 4 ) and the wobble plate ( 5 ), the swash plate ( 4 ) and the wobble plate ( 5 ) having been joined to one another during assembly of the bearing to form an integrated bearing unit from which the bearing ( 7 ) cannot be separately detached. Advantageously, the bearing ( 7 ) comprises two races ( 20, 22:26, 22 ) between which is located a plurality of rolling bearings ( 23 ) and at least one ( 22:26 )) of the two races of the bearing ( 7 ) is integrally formed with either the swash plate ( 4 ) or the wobble plate ( 5 ), preferably with the wobble plate ( 5 ).

[0001] The present invention relates to a wobble plate arrangement for a swash plate compressor, in particular a CO₂ compressor, for a vehicle air-conditioning system, and to a compressor incorporating such an arrangement.

[0002] DE 198 33 604 A1 describes a swash plate compressor for a vehicle air-conditioning system which has a wobble plate arrangement between the pistons of the compressor and a drive shaft. The wobble plate is coupled to the swash plate via a thrust bearing and a shoulder bearing or angular ball bearing. As the wobble plate in this compressor is made of a light alloy, the inner and outer faces of the bearings must be made from stronger inserts. In the case of the thrust bearing, a thin axial disk is inserted to form the bearing face on the wobble plate whereas in-the case of the shoulder bearing or angular ball bearing a thin ring-type bearing face is used. The latter allows the predetermined radial assembly space between the connecting rod seat in the wobble plate and the swash plate to be utilized.

[0003] Conventional angular contact bearings tend to employ large diameter balls and, with a view to the adjustability of bearing and mechanical friction, a bearing with comparatively larger but fewer balls is to be preferred.

[0004] U.S. Pat. No. 5,826,490 also describes a compressor with a wobble plate arrangement which comprises a swash plate on which a wobble plate is rotatably mounted. In order to permit the take-up of forces and moments by the driving mechanism of the compressor there are three bearing sites provided with two needle thrust bearings and a needle radial bearing.

[0005] The object of the present invention is to provide a wobble plate arrangement for a swash plate compressor which can be manufactured economically and which optimizes as far as possible the features of strength, bulk, size, number of components, work tolerances, and ease of assembly for use in a compressor for a vehicle air conditioning arrangement.

[0006] According to a first aspect of the present invention there is provided a wobble plate arrangement for a swash plate compressor comprising a swash plate on which a wobble plate is rotatably mounted and at least one antifriction bearing being located therebetween, characterized in that the swash plate and the wobble plate are joined to one another during assembly of the bearing to form an integrated bearing unit from which the bearing cannot be separately detached.

[0007] Preferably, the bearing comprising two races between which is located a plurality of rolling bearings, and at least one of the two races of the bearing is integrally formed with either the swash plate or the wobble plate.

[0008] Hence, the wobble plate has two degrees of rotary freedom as it can rotate jointly with the swash plate and also rotate relative to the swash plate.

[0009] Preferably also, one of the races of the bearing is integrally formed with the wobble plate, the bearing being located between apposed circumferential faces of the swash plate and the wobble plate.

[0010] The bearing is preferably located between apposed circumferential faces of the swash plate and the wobble plate and in a first embodiment an insert defining an inner race is fitted to the swash plate. Preferably, the profile of the inner race flares radially outwardly to enable the play of the bearing to be adjusted by axial adjustment of the position of the insert. Advantageously, the insert is retained in position by a lip formed from the swash plate by a cold shaping process.

[0011] Preferably, in a second embodiment of the invention, an outer race of the bearing is integrally formed with the wobble plate and an inner race of the bearing is integrally formed with the swash plate. The axial play of this bearing is preferably adjusted by a thermal contraction or expansion of the swash plate or the wobble plate.

[0012] Preferably also, the rolling bearings are retained in position by the insertion of a cage, which may be made of welded steel or other material such as a polyamide.

[0013] Preferably also, the wobble plate and the swash plate are made from tempered steel and any races integral with these plate are formed by a mechanical polishing of the plate. Alternatively the wobble plate is made from a light metal which has been coated with another material such as a ceramic outer layer.

[0014] The bearing preferably comprises one of a single-row radial ball bearing, a double-row radial ball bearing, and a deep groove ball bearing.

[0015] According to a second aspect of the present invention there is provided a compressor for a vehicle air conditioning system comprising a wobble plate arrangement according to the first aspect of the invention.

[0016] According to a third aspect of the present invention there is provided a compressor for a vehicle air conditioning system comprising at least one piston moveable in a cylinder, a drive shaft, a wobble plate arrangement comprising a swash plate on which a wobble plate is rotatable mounted located between the piston and the drive shaft, and at least one antifriction bearing being located between the swash plate and the wobble plate, and characterised in that the swash plate and the wobble plate have been joined to one another during assembly of the bearing to form an integrated bearing unit from which the bearing cannot be separately detached.

[0017] The various aspects of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0018]FIG. 1 is a longitudinal cross-sectional view of a first embodiment of wobble plate arrangement according to the present invention shown mounted on a shaft of a compressor and connected to a piston of the compressor;

[0019]FIG. 2 is view similar to FIG. 1 of a second embodiment of wobble plate arrangement; and

[0020]FIG. 3 is a schematic transverse cross-sectional view of the second embodiment of wobble plate arrangement during manufacture.

[0021] In the following description the same reference numerals are used for the same or equivalent components of the invention and associated apparatus.

[0022] As shown in the FIGS. 1 and 2, a wobble plate arrangement 1 according to the invention for a compressor is arranged between a plurality of pistons 2 and a drive shaft 3, driving of the pistons 2 being effected by the wobble plate arrangement 1. The wobble plate arrangement 1 comprises a swash plate 4 on which a wobble plate 5 is rotatably mounted. The wobble plate 5 is able to rotate freely with respect to the swash plate 4, antifriction bearings 6 and 7, as will be described in more detail below, being provided between the swash plate 4 and the wobble plate 5. The wobble plate 5 is also able to rotate freely with respect to the pistons 2, another bearing 8 being provided which allow movement of the wobble plate 5 relative to the pistons 2 in a circumferential direction.

[0023] The swash plate 4 is rotatably driven by the drive shaft 3 by means of a base plate 9 which is connected to the drive shaft 2 and thereby rotates therewith and to an articulated arm 10 that also rotates as the base plate 9 rotates. The articulated arm 10 is connected to-the swash plate 4 at a swivel point 11.

[0024] In order to reduce the stroke of the pistons 2, the swash plate 5 is not only able to swivel about the swivel point 11 but also to rotate about a swivel point 12 of a guide arrangement 13 which is displaceable axially on the drive shaft 2 and loaded by a compression spring 14. Hence, a the drive shaft 2 rotates, the base plate 9 and the articulated arm 10 connected thereto rotate and the latter drives the swash plate 4. Rotation of the swash plate 4 sets the wobble plate 5 into a wobbling motion to drive the pistons 2.

[0025] In a first embodiment as shown in FIG. 1, the bearing 6 comprises a roller bearing located between apposed radially extending faces 15 and 16 of the swash plate 4 and the wobble plate 5 respectively. It will be appreciated that the rollers 17 of the bearing 6 are only subjected to loads perpendicular to their axis of rotation. However, the bearing 7 is located between apposed circumferential faces 18 and 19 of the swash plate 4 and the wobble plate 5 and comprises a single-row grooved ball bearing which can take some thrust loads in addition to considerable radial load.

[0026] The bearing 7 comprises an inner race 20 formed by an insert that is connected to an axially extending portion 21 of the swash plate 4 and rotates therewith. An outer race 22 is provided by an appropriately profiled surface of the wobble plate 5 opposite the race 20. The outer race 22 is thereby integrally formed with the wobble plate 5 and a separate insert to provide the outer race is not therefore required. The rolling bearings comprise balls 23 which are located between the inner and outer races 20 and 22 and retained in position by a cage 24. The cage 24 may comprise a welded steel cage or be made of a synthetic material such as polyamide. As the cage 24 holds the balls 23 in position, its insertion thus prevents the swash plate and the wobble plate from being detached from one another.

[0027] In view of the integration of the outer race 22 of the bearing with the wobble plate 5, it is necessary for the wobble plate 5 to be manufactured from a higher-strength material than the light alloys conventionally used for such plates. A suitable material for the purpose is tempered steel and the outer race 22 is preferably formed by a mechanical superfinishing or polishing of the previously profiled surface. Alternatively, the wobble plate 5 is made from a light metal which is strengthened by plating it with stronger material. For example it could be coated with a ceramic outer layer by thermal spraying. The swash plate 4 is preferably made from tempered steel.

[0028] The inner race 20 of the bearing 7 is located and retained in position during a cold shaping process wherein a portion of the swash plate 4 is formed to provide an annular lip 25 which holds the race 20 in position. This also enables the bearing to be prestressed. The profile of the inner race 20 is preferably flared radially outwards as shown in FIG. 1. In this way the axial clearance of the bearing 7 can be adjusted very precisely by axial adjustment of the position of the insert defining the race 20 during fitment. This is necessary because it will be appreciated that the bearing 7 is not manufactured separately but forms an integral part of the wobble plate arrangement 1 and is assembled as the arrangement 1 is itself assembled. To ensure a useful life for the bearing 7 and to ensure a quiet running of the compressor it is essential that the bearing clearance, that is the axial play between the races 20 and 22, be adjusted accurately.

[0029] During manufacture, the balls 23 are inserted into the assembly on one side into the outer race 22 of the wobble plate 5. The swash plate 4 and associated inner race 20 are then inserted axially along the longitudinal axis of the wobble plate 5. The balls 23 are then distributed appropriately around the circumference of the bearing 7 before the cage 24 is inserted to hold them into place. The inner race 20 is then located, adjusted correctly and then retained by the cold shaping process which forms the lip 25.

[0030] The wobble plate arrangement 1 is thus manufactured as a sealed unit so that the bearing 7 cannot not be disassembled. In this way the swash plate 4 and the wobble plate 5 are joined to one another during assembly to form a bearing unit.

[0031] It is also possible for the bearing 7 to comprise a single-row or a double-row radial or deep groove ball bearing. Such an arrangement would be capable of taking up considerable axial forces. The compression spring 14 could also be integrated into the assembly, which would reduce considerably the assembly time of the compressor as a whole.

[0032] In a second embodiment as shown in FIG. 2, an inner race 26 of the bearing 7 is provided as an integral part of the swash plate 4, obviating the requirement for the insert 20. In this case, as with the outer race 22, the inner race 26 is preferably formed by a mechanical superfinishing or polishing of the previously profiled surface or a tempered steel swash plate 4. The assembly of such an arrangement will now be described with reference to FIG. 3.

[0033] During the manufacture, the wobble plate 5 is profiled to provide the outer race 22 as previously described with reference to FIG. 1. Then during assembly of the bearing unit, the rolling bearings comprising the balls 23 are located side by side on the race 22 substantially in one half of the circumference of the race 22 as shown in FIG. 3. The swash plate 4 with its integral inner race 26, which is also formed by an appropriately undercut surface of the plate 4, is inserted eccentrically into the annulus defined by the wobble plate 5 along a longitudinal axis 27 that is offset but parallel to the longitudinal axis 28 of the wobble plate 5. The swash plate 4 is then loaded axially against the wobble late 5, the bearing 6 being located between the apposed radially extending faces 15 and 16 of the swash plate 4 and the wobble plate 5 respectively. The balls 23 are then be distributed around the circumference of the wobble plate 5. This action removes the eccentricity of the swash plate 4 and bring the axes 27 and 28 into coincidence. The balls 23 are then distributed evenly between the two races 22 and 26 and fixed in position by the insertion of the cage 24 (not shown in FIG. 3) into the gap between the races 22 and 26.

[0034] It will be appreciated that using this method of assembly, the number of balls 23, their size an the depth of the undercuts used to produce the races 22 and 26 are all variable.

[0035] In an alternative method of manufacture, the balls 23 may be inserted between the races 22 and 26 via a feed channel (not shown) which is provided in either the swash plate 4 or the wobble plate 5 in the region of the race 25 or 26 respectively.

[0036] As with the first embodiment, it will be appreciated that such a wobble plate arrangement 1 also forms an integrated bearing unit with no separate bearing attachments. This has the advantage of reducing the size of the arrangement 1 and of obviating the loosening and settling of bearing attachment components which takes place during use.

[0037] The bearing clearance must therefore also be finely adjusted to an optimal clearance for the same reasons as mentioned above in connection with the first embodiment. The bearing clearance between the races 22 and 26 is adjusted during assembly of the unit by either contracting the wobble plate 5 by cooling or expanding the swash plate 4 by heating thus enabling the two components of the bearing unit to be assembled and adjusted well. At temperature equilibrium, the bearing unit is adjusted with relatively little clearance.

[0038] Advantageously in both embodiments, the swash plate 3 or the wobble plate 4 or both are either molded or forged pieces. A large-scale mass production of such pieces permits there to be a high size accuracy of the pieces so that little finishing work, such as machining, is required.

[0039] The bearings 6 and 7 may be varied as required. Preferably, the combination is as previously descried, bearing 6 comprising a roller bearing, such as a needle roller bearing, and bearing 7 comprising an angular ball bearing. However, it is also possible to pair an axial roller bearing with one or more radial groove ball bearing, which may have one or double rows. The integrated bearing unit may thus comprise up to three bearings. It would also be possible to use two shoulder ball bearings, each with different pressure absorption angles.

[0040] Hence, the wobble plate 5 may be profiled to define a total of four bearing races and the swash plate 4 may be profiled to define a total of up two bearing races.

[0041] The invention enables the space required for the bearing 7 to be considerably reduced and the setting of the bearing clearance to be simplified. Advantageously, less close tolerance work is required. Also, it is possible to use large ball bearings 23, which means that fewer balls need to be used and the friction generated is thereby also reduced.

[0042] Overall, the invention provides for a reduction in the number of components required and less assembly line effort than conventional arrangements, which keep costs low and increases the efficiency of production. 

1. A wobble plate arrangement (1) for a swash plate compressor comprising a swash plate (4) on which a wobble plate (5) is rotatably mounted and at least one antifriction bearing (7) being located therebetween characterized in that the swash plate (4) and the wobble plate (5) are joined to one another during assembly of the bearing (6, 7) to form an integrated bearing unit from which the bearing (6, 7) cannot be separately detached.
 2. An arrangement as claimed in claim 1, wherein the bearing (7) comprises two races (20, 22; 26, 22) between which is located a plurality of rolling bearings (23), characterized in that at least one of the two races (20, 22:26, 22) of the bearing (7) is integrally formed with either the swash plate (4) or the wobble plate (5).
 3. An arrangement as claimed in claim 2, characterized in that one (22) of the two races (20, 22:26, 22) of the bearing (7) is integrally formed with the wobble plate (5).
 4. An arrangement as claimed in claim 2 or claim 3, characterized in that the bearing (7) is located between apposed circumferential faces (15, 16) of the swash plate (4) and the wobble plate (5).
 5. An arrangement as claimed in claim 4, characterized in that an insert (20) defining an inner race is fitted to the swash plate (4).
 6. An arrangement as claimed in claim 4, characterized in that the profile of the inner race (20) flares radially outwards to enable the play of the bearing (7) to be adjusted by axial adjustment of the position of the insert (20).
 7. An arrangement as claimed in claim 5 or claim 6, characterized in that the insert (20) is retained in position by a lip (25) formed by the swash plate (4).
 8. An arrangement as claimed in claim 7, characterized in that the lip (25) is formed from the swash plate (4) by a cold shaping process.
 9. An arrangement as claimed in claim 4, characterized in that an outer race (22) of the bearing (7) is integrally formed with the wobble plate (5) and an inner race (26) of the bearing (7) is integrally formed with the swash plate (4).
 10. An arrangement as claimed in claim 9, characterized in that the bearing unit is assembled by inserting the swash plate (4) eccentrically into the annulus defined by the wobble plate (5) along a first longitudinal axis (27) that is offset but parallel to a second longitudinal axis (28) of the wobble plate (5).
 11. An arrangement as claimed in claim 10, characterized in that the rolling bearings (23) are distributed between the inner and outer races (22, 26) to remove the eccentricity of the swash plate (4) and to bring the first and second longitudinal axes (27, 28) into coincidence.
 12. An arrangement as claimed in claim 9, characterized in that the rolling bearings (23) are distributed between the inner and outer races (22, 26) via a feed channel provided in either the swash plate (4) or the wobble plate (5).
 13. An arrangement as claimed in any of claims 9 to 12, characterized in that the axial play of the bearing (7) is adjusted by a thermal contraction or expansion of the swash plate (4) or the wobble plate (5).
 14. An arrangement as claimed in any of claims 2 to 13, characterized in that the rolling bearings (23) are retained in position by the insertion of a cage (24) between the two races (20, 22:26, 22) of the bearing.
 15. An arrangement as claimed claim 14, characterized in that the cage (24) comprises welded steel cage or a polyamide cage.
 16. An arrangement as claimed in any one of claims 1 to 15, characterized in that the wobble plate (5) is made from tempered steel.
 17. An arrangement as claimed in any one of claims 1 to 16, characterized in that the wobble plate (5) defines one (22) of the two races of the bearing (7), the race (22) being formed by a mechanical polishing of the wobble plate (5).
 18. An arrangement as claimed in any one of claims 1 to 15, characterized in that the wobble plate (5) is made from a light metal which has been coated with another material.
 19. An arrangement as claimed in claim 18, characterized in that the wobble plate (5) is coated with a ceramic outer layer.
 20. An arrangement as claimed in any one of claims 1 to 19, characterized in that the swash plate (4) is made from tempered steel.
 21. An arrangement as claimed in any one of claims 1 to 20, characterized in that the swash plate (4) defines one (26) of the two races of the bearing (7), the race (26) being formed by a mechanical polishing of the swash plate (4).
 22. An arrangement as claimed in any one of claims 1 to 21, characterized in that the bearing (7) comprises one of a single-row radial ball bearing, a double-row radial ball bearing, and a deep groove ball bearing.
 23. An arrangement as claimed in any one of claims 1 to 22, characterized in that two anti-friction bearings (6, 7) are located between the swash plate (4) and the wobble plate (5).
 24. An arrangement as claimed in claim 23, characterized in that the two anti-friction bearings (6, 7) respectively comprise an axial roller bearing (6) and an angular ball bearing (7).
 25. An arrangement as claimed in claim 23, characterized in that the two anti-friction bearings (6, 7) comprise two single-row angular ball bearings.
 26. An arrangement as claimed in claim 23, characterized in that the two anti-friction bearings (6, 7) respectively comprise an axial roller bearing and an single-row ball bearing.
 27. An arrangement as claimed in claim 23, characterized in that the two anti-friction bearings (6, 7) respectively comprise an axial roller bearing and a double-row ball bearing.
 28. An arrangement as claimed in claim 23, characterized in that the integrated bearing unit comprises up to three bearings.
 29. An arrangement as claimed in claim 23, characterized in that the wobble plate (5) is profiled to define a total of four bearing races.
 30. An arrangement as claimed in claim 23, characterized in that the swash plate (4) is profiled to define a total of up two bearing races.
 31. An arrangement as claimed in any one of claims 1 to 30 characterized in that the wobble plate (5) has two degrees of rotary freedom so that it can rotate jointly with the swash plate (4) and rotate relative to the swash plate (4).
 32. A compressor for a vehicle air conditioning system characterized in that it comprises a wobble plate arrangement (1) as claimed in any one of claims 1 to
 31. 33. A compressor for a vehicle air conditioning system comprising at least one piston (2) moveable in a cylinder, a drive shaft (3), a wobble plate arrangement (1) comprising a swash plate (4) on which a wobble plate (5) is rotatable mounted located between the piston (2) and the drive shaft (3), and at least one antifriction bearing (7) being located between the swash plate (4) and the wobble plate (5), characterised in that the swash plate (4) and the wobble plate (5) have been joined to one another during assembly of the bearing to form an integrated bearing unit from which the bearing (7) cannot be separately detached. 